Automatic phonograph record changer



July 15, 1947. 2,424,132

H. v. ALEXANDERSSON AUTOMATIC PHONOGRAPH RECORD CHANG ER 7 Filed Feb. 9, 1945 INVENTOR- Patente d July 15, 1947 AUTOMATIC PHONOGRAPH RECORD CHANGER Harald Valdemar Alexandersson, Lidingo, Sweden, assignor to Aga-Baltic Aktiebolag, Stockholm, Sweden, a corporation of'Sweden Application February 9, 1943, Serial No. 415,246

3 Claims.

My invention relates to automatic recordchangers for phonographs.

In devices of this type it is necessary that, after the record-changing having been completed, the tone arm carrying the needle should be lowered in such a way that the latter enters the initial groove of the new record. However, it is known that the actual diameter of different records may vary a few millimeters even if the records are said to have the same diameter, and further that the edge spacing on the records, which does not contain any reproduction groove, may also vary in width a few millimeters. Consequently, if the needle is always lowered on to the record at the same radius, independently of the actual diameter of the latter, it may occur that the needle is lowered into th second, third or even the fourth turn of the reproduction groove if the groove begins too far out on th record, whereas in the opposite case the needle may be lowered on to the edge part of the record, which does not contain any reproduction groove. In the former case the beginning of the music will not be reproduced, whereas in the opposite case the needle may run a plurality of turns on the smooth edge part without entering the groove. Dependent upon the angle of incidence of the tone arm against the record it may even occur that the needle will continuously remain on said smooth edge part or be thrown outwards, so that it falls down onthe turntable, in which case there is danger of tearing the felt covering of the latter.

In newer records, in order to avoid this difiiculty, there is often provided a so-called entrance groove, which extends with a greater than normal pitch from the outmost edge of the record to the initial turn of the reproduction groove. Hence, if the needle is lowered into the smooth edge, it hits this entrance groove as the record is rotated, and is thus guided inwards to the reproduction groove.

As a rule the last named arrangement is a sufficient means for preventing damage to the felt on the turntable. On the other hand it means a certain delay added to the time required by the record-changing itself. Finally, it is frequently desired to play older records which are not provided with such an entrance groove.

The present invention refers to an arrangement in connection with the record-changer itself, by which the needle is given an impulse for moving it towards the centre of the record. The invention is applied to record-changers in which the movement of the tone arm is controlled by means of a cam disc, a groove disc or the like. Such Sweden August 22, 1942- cam or groove discs are usually divided in two different parts, radially separated from each other. One part contains the cam surface or the groove by means of which the swinging out and inwards of the tone arm during the recordchanging is controlled, whereas the other part frees the tone arm for movement so that the needle may follow the spiral groove during the reproduction of the record.

According to the invention, there is arranged a spring on the cam disc, which is placed at the end of the cam surface or groove which moves the tone arm during record changing the spring being arranged to strike the cam follower which controls the tonearm, so as to give the follower and hence the arm an impulse for movement towards the centre of the record. This impulse, however, is not strong enough to move the tone arm if the needle has entered the groove in the record.

The invention is further described On the annexed drawing, in which Fig. 1 is a plan view of the essential parts of an automatic record-changing arrangement in accordance with the present invention, whereas Fig. 2 shows an enlargement of a detail of the arrangement according to Fig. 1.

In the arrangement shown in the drawing, it is assumed that the movement of the sweep arm H] is controlled by means of a cam disc ll, turnable about a centre pin [2. In well-known manner the cam disc is rotated during the record-changing in the direction of the arrow.l3 by means of a roller l4 driven by the phonograph motor, which roller rides up on to the surface l5 of the cam disc ll. During the reproduction of the record the disc II is stationary, the roller 14 rotating freely in a recess I6 in this surface. The control of the arm In by means of the groove I! in the cam disc takesplace by means of a cam follower in the form of a pin l8, which is connected to an arm 2U pivotable about a point H1. The arm 20 is by means of a link 2| connected to the sweep arm II].

In the position shown in the drawing the pin 18 is in the enlarged part 22 of the groove, which permits free movement of the sweep arm l8 during the reproduction of the record. After a record has been reproduced the cam disc H is rotated in the direction of the arrow l3, whereby the pin I8 is guided into the opening of the groove l1 and follows this groove into one of the groove parts 23 or 24, dependent upon the position of a track switch member 25. The last named arrangement is provided in order to properly position the tone arm for playing small or large records. The arrangements for the control of the track switch 25 form no part of the present invention.

According to the invention, however, in the place where the groove parts 23 and 24 open into the enlarged part 22 there are arranged springs 26 and 26, respectively, for each of the. two groove parts, the arrangement of'which is more evident from the detail Figure 2, which shows one of the springs.

In the form of execution of the invention shown in Fig. 2 the cam disc H is provided with a pin 21 and an opening 28. One end of. the spring 25 is bent angularly and extends into the opening 28, whereby this end of the spring is. fixed against pivotal movement, about the, pin

' 21. The spring is wound one or more turns spir= ally about the pin 21, and its other end extends fully or partly across the end of the grooveii23 or 24, respectively. The spring 26 is of such strength that it gives the pin [8 an impulse for movement towards, the centre of the cam disc. l2 immediately after it leaves one of. the grooves 23 or 24 and as it enters the enlarged part 22, which impulse is transferred to the arm which indirectly moves the reproduction needle. Consequently, the latter is moved inwards until it is stopped by the outmost reproduction groove of the record.

Of course, the invention is not limited to the formv of execution shown in the figure in detail and described in the specification, but certain modificationsmay be made which will be evident to the man skilled in the art and the invention, of course, comprises all such modified arrangements.

What is claimed is:

1. For use in a phonograph of the record changer type for moving the phonograph needle.

into the first sound groove, a cam disc having a cam groove therein, a cam follower for operating in. said groove, said groove having; a portion, of narrow gage for confining saidfollowerto a precise path of travel, and having a portion of wider gage permitting reater movement of said follower, a spring located adjacent the junction, of said portions and extending obliquely inward across the path of travel of said follower immediately after the latter has left said portion of narrow gage and has entered said portion of wider gage whereby said follower is given an impulse tending to resiliently move it inwardly.

2. For use in a phonograph of the record changer type for moving the phonograph needle into the first sound groove, a cam disc: having a cam groove therein, a cam follower for operating in said groove, said groove having a portion of narrow gage for confining said follower to a precise path of travel, and having a portion of wider gage permitting greater movement of said follower, a pin carried by said cam disc adjacent to said juncture, a recess in said disc spaced from said pin in a direction away from said portion of wide gage, a spring member having a coiled central part embracing'said pin, one end portion of said spring extending into said recess and the other end portion of the spring extending obliquely inward across the path of travel of said follower. immediately after the latter has left said portion of'narrow gage andhas entered said por tion of wider gage. whereby said follower is, given an impulse tending to resiliently move it inwardly.

3. For use in a phonograph of. the record changer type for moving the phonograph needle into the first sound groove, control mechanism comprising a body having means defining a path of travel and including aportion of narrow gage and a portion of. wider gage, a follower arranged.

to travel insaid path, spring. means disposed ad-- jacent the junction of said portions obliquely inward across the'path of travel of said follower immediately after it has left the portion of narrow gage and has entered the portion of wider gage'for imparting an impulse tending to resilie'ntlymovesaid follower inwardly of. said path.

HARALD VALDEMAR ALEXANDERSSON.

REFERENCES CITED The. following references are of record in the file of this patent? UNITED STATES PATENTS. 

